The invention concerns a medical instrument and in particular a method for filling a hollow space in an autoclavable medical instrument with an adhesive containing a filler.
In the production of medical appliances, it is customary, when assembling the instrument, for certain structural parts to be connected to one another or imbedded using an adhesive seal. The first purpose of the adhesive seal is to position and fix the structural parts relative to one another, which is achieved by the cured adhesive. Another important point is to ensure a sealed connection between these structural parts, in order to avoid contaminants from the outside being able to penetrate into the interior of the instrument. Such contaminants can include body fluids or tissue fluids with which the medical instrument comes into contact during surgical use. However, contaminants can also include gaseous or liquid cleaning agents that are used in the cleaning and sterilizing procedures carried out after the medical interventions. These can be very aggressive cleaning agents, for example cleaning agents containing peroxide. Moreover, during autoclaving, in particular during what is called flash autoclaving, the instruments are heated to temperatures in access of 145° C. and are very rapidly cooled down again. In practical application, it has now be found that these extreme loads which act repeatedly on a surgical instrument, for example a frequently used endoscope, gradually leads to cracks in the adhesive seal.
This results not only from the extreme thermal loads or stresses that arise during the autoclaving itself. Instead, the formation of cracks is also promoted by the fact that the adhesive, which is composed of a cured plastic material, mostly fills space between metal materials, in most cases medical-grade steel. These metallic materials have different thermal properties than the adhesive as such. Not only can cracks develop in the adhesive itselves for this reason, but the adhesive also partially detaches itself from the contact face with the mostly metal material that is cast with the adhesive.
In long-term applications, therefore, contaminants can gradually penetrate from the outside through these cracks into the interior of the medical instrument. These contaminants compromise the operating safety of the instrument.
From British patent specification 1,122,672 a medical instrument which is a mouth mirror is known. A distal mounting plate serves for mounting a mirror via an adhesive to the mounting plate. The adhesive is mixed with a metal powder, for example iron powder or aluminum powder. Due to this the thermal conductivity of the adhesive is enhanced remarkably. With that method thermal stresses can be reduced with the result, that there is no risk that the mirror releases from the mounting plate after several sterilization processes.
It is an object of the present invention to provide a method for filling a hollow space in an autoclavable medical instrument with an adhesive containing a filler allowing the filler particles to come very close together in the resulting composite.
It is further an object of the present invention to provide an autoclavable medical instrument having a hollow space therein said hollow space being filled with a composite containing a cured adhesive having distributed solid particles therein.